1. Field of the Invention
The present invention generally relates to semiconductor devices. More specifically, the present invention relates to a semiconductor device including a current mirror circuit.
2. Description of the Related Art
Conventionally, current mirror circuits formed by transistors have been used as parts of various circuits. The current mirror circuit includes two transistors. An electric current having a designated rate flows to each of the transistors. In such a current mirror circuit, if there is unevenness in electric characteristics between the transistors, the electric current having the designated rate cannot flow. Because of this, the current mirror circuit is formed by transistors having equal channel lengths and channel widths so that characteristics of the transistors are the same. See, for example, Japanese Laid-Open Patent Application Publication No. 2007-318094.
However, the electric current having the designated rate may not flow by only making the characteristics of the transistors the same. In other words, in the semiconductor device where the current mirror circuit is formed, due to parasitic resistance of a metal wiring or the like connected to the current mirror circuit, the rate of the electric current flowing to each of the transistors may be shifted from a designated rate.